"The Baptism of Christ" by Domenikos Theotokopoulos, commonly known as El Greco is displayed at Christies auctioneers October 20, 2004 in London. The painting, by one of Europe's most renowned Old Master artists, was found in an envelope during a routine valuation and is expected to fetch 400,000-600,000 GBP when it is auctioned in December.

The painting, dating from the years when El Greco moved from his native Crete to Venice, was found in a brown envelope in an upstairs apartment in the west of Spain, Christie's spokesman Matthew Paton said. It was inherited by a family that responded to a Christie's advertisement about the London-based auction house's evaluation services, he said in an interview.

Discoveries of such valuable artworks aren't common, though a Sotheby's Holdings Inc. specialist in March found Raphael's ``Head of a Child'' chalk drawing. The El Greco will be part of Christie's second-biggest London Old Master sale of the year, which may bring in as much as 10 million pounds, Paton said.